US4180979A — Anti-stall control for electrical hydrostatic tra…

Claim 1

Independent Claim 143 words

In a control system for a hydrostatic transmission of the type including an engine driven variable displacement fluid pump, the control system including main control means operable in response to an electrical input command signal to vary the displacement of the fluid pump, command signal generator means for generating an operative command signal, means providing a first electrical input signal representative of actual engine speed, and means providing a second electrical signal representative of unloaded engine speed, the improvement comprising: (a) means for comparing said first and second electrical input signals and generating an electrical anti-stall signal representative of the maximum percentage of instantaneously commanded pump displacement which is permissible without causing the engine to drop below a predetermined minimum engine speed; and (b) means for electrically multiplying said anti-stall signal and said operative command signal to generate a reduced input command signal.

Claim 2

Dependent Claim 143 words

In a control system for a hydrostatic transmission of the type including an engine driven variable displacement fluid pump, the control system including main control means operable in response to an electrical input command signal to vary the displacement of the fluid pump, command signal generator means for generating an operative command signal, means providing a first electrical input signal representative of actual engine speed, and means providing a second electrical signal representative of unloaded engine speed, the improvement comprising: (a) means for comparing said first and second electrical input signals and generating an electrical anti-stall signal representative of the maximum percentage of instantaneously commanded pump displacement which is permissible without causing the engine to drop below a predetermined minimum engine speed; and (b) means for electrically multiplying said anti-stall signal and said operative command signal to generate a reduced input command signal.

Claim 3

Dependent Claim 43 words

The improvement as claimed in claim 1 wherein said multiplying means comprises electronic switching means operable to switch its output between said operative command signal and a reference signal representative of a minimum pump displacement in response to changes in said anti-stall signal.

Claim 4

Dependent Claim 31 words

The improvement as claimed in claim 1 or 2 wherein said anti-stall signal comprises a substantially square-wave having a duty cycle approximately equal to said maximum permissible percentage of pump displacement.

Claim 5

Dependent Claim 23 words

The improvement as claimed in claim 1 wherein said command signal generator means includes rate limiting circuit means and signal shaping circuit means.

Claim 6

Dependent Claim 172 words

In a control system for a hydrostatic transmission of the type including an engine driven fluid pump and a fluid motor, one of said pump and said motor being of the variable displacement type, the control system including main control means operable in response to an electrical input command signal to vary the displacement of the variable one of the pump and motor, command signal generator means for generating an operative command signal, means providing a first electrical input signal representative of actual engine speed, and means providing a second electrical input signal representative of unloaded engine speed, the improvement comprising: (a) means for comparing said first and second electrical input signals and generating an electrical anti-shall signal having a gain between 0.0 and 1.0, the gain being representative of a percentage change in the instantaneously commanded swashplate displacement necessary to prevent the engine speed from dropping below a predetermined minimum; and (b) means for electrically multiplying said anti-stall signal and said operative command signal to generate a modified input command signal.

Claim 7

Dependent Claim 172 words

In a control system for a hydrostatic transmission of the type including an engine driven fluid pump and a fluid motor, one of said pump and said motor being of the variable displacement type, the control system including main control means operable in response to an electrical input command signal to vary the displacement of the variable one of the pump and motor, command signal generator means for generating an operative command signal, means providing a first electrical input signal representative of actual engine speed, and means providing a second electrical input signal representative of unloaded engine speed, the improvement comprising: (a) means for comparing said first and second electrical input signals and generating an electrical anti-shall signal having a gain between 0.0 and 1.0, the gain being representative of a percentage change in the instantaneously commanded swashplate displacement necessary to prevent the engine speed from dropping below a predetermined minimum; and (b) means for electrically multiplying said anti-stall signal and said operative command signal to generate a modified input command signal.

Claim 8

Dependent Claim 26 words

The improvement as claimed in claim 1 or 5 wherein said comparing and generating means includes means providing an oscillating signal having a substantially constant frequency.

Claim 9

Dependent Claim 44 words

The improvement as claimed in claim 6 wherein said comparing and generating means further includes means providing a signal which is a weighted summation of said first electrical input signal and said oscillating signal, said summation signal having an alternately increasing and decreasing magnitude.

Claim 10

Dependent Claim 36 words

The improvement as claimed in claim 7 wherein said comparing and generating means further includes electrical comparator circuit means for comparing said second electrical input signal and said summation signal and generating said electrical anti-stall signal.

Claim 11

Dependent Claim 63 words

The improvement as claimed in claim 8 wherein said anti-stall signal comprises a substantially square-wave signal, alternating between maximum and minimum magnitudes, said electrical anti-stall square-wave signal having one of said magnitudes when said summation signal is greater than said second electrical input signal and having the other of said magnitudes when said summation signal is less than said second electrical input signal.

Claim 12

Dependent Claim 26 words

The improvement as claimed in claim 7 wherein said means providing said weighted summation signal includes means for adjusting the weight factor of said summation signal.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1982-12-31	1983-07-02	1984-01-01	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1986-12-31	1987-07-02	1988-01-01	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1990-12-31	1991-07-02	1992-01-01	$7700.00	Window Closed / Lapsed

Anti-stall control for electrical hydrostatic transmission control system

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